TROJ_CRYPDEF.BUB
Ransom:Win32/Crowti (Microsoft); Trojan-Ransom.Win32.Blocker.ftxq (Kaspersky); Trojan.Cryptodefense (Symantec)
Windows
Threat Type: Trojan
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It deletes itself after execution.
TECHNICAL DETAILS
314,368 bytes
EXE
Yes
04 Oct 2014
Arrival Details
This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
Installation
This Trojan adds the following folders:
- %System Root%\{7 characters from UID}
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
It drops the following copies of itself into the affected system:
- %System Root%\{7 characters from UID}\{7 characters from UID}.exe
- %Application Data%\{7 characters from UID}.exe
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)
Autostart Technique
This Trojan adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{6 characters from UID} = "%System Root%{7 characters from UID}\{7 characters from UID}.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{7characters from UID} = "%Application Data%\{7 characters from UID}.exe"
It enables its automatic execution at every system startup by dropping the following copies of itself into the Windows Common Startup folder:
- %User Startup%\{7 characters from UID}.exe
(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)
Other System Modifications
This Trojan modifies the following file(s):
- database files
- web files
- MS Office files
- video
- images
- script files
- text files
- other non-binary files
It adds the following registry keys:
HKEY_CURRENT_USER\Software\{UID}
HKEY_CURRENT_USER\Software\{UID}\
{16 alphanumeric characters}
It modifies the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SystemRestore
DisableSR = "1"
(Note: The default value data of the said registry entry is "0".)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\BITS
Start = "4"
(Note: The default value data of the said registry entry is "3".)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\ERSvc
Start = "4"
(Note: The default value data of the said registry entry is "2".)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wscsvc
Start = "4"
(Note: The default value data of the said registry entry is "2".)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wuauserv
Start = "4"
(Note: The default value data of the said registry entry is "2".)
Other Details
This Trojan connects to the following possibly malicious URL:
- http://{BLOCKED}ntin.com
It deletes itself after execution.
NOTES:
This Trojan drops the following files in all folders:
- DECRYPT_INSTRUCTION.TXT
- DECRYPT_INSTRUCTION.HTML
- DECRYPT_INSTRUCTION.URL
SOLUTION
9.700
11.170.03
25 Sep 2014
11.171.00
26 Sep 2014
Step 1
Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.
Step 2
Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.
Step 3
Restart in Safe Mode
Step 4
Delete this registry value
Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- {6 characters from UID} = "%System Root%{7 characters from UID}\{7 characters from UID}.exe"
- {6 characters from UID} = "%System Root%{7 characters from UID}\{7 characters from UID}.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- {7characters from UID} = "%Application Data%\{7 characters from UID}.exe"
- {7characters from UID} = "%Application Data%\{7 characters from UID}.exe"
Step 5
Delete this registry key
Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
- In HKEY_CURRENT_USER\Software
- {UID}
- {UID}
Step 6
Restore this modified registry value
Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRestore
- From: DisableSR = "1"
To: DisableSR = "0"
- From: DisableSR = "1"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BITS
- From: Start = "4"
To: Start = "3"
- From: Start = "4"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ERSvc
- From: Start = "4"
To: Start = "2"
- From: Start = "4"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wscsvc
- From: Start = "4"
To: Start = "2"
- From: Start = "4"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wuauserv
- From: Start = "4"
To: Start = "2"
- From: Start = "4"
Step 7
Search and delete this folder
- %System Root%\{7 characters from UID}
Step 8
Search and delete this file
- DECRYPT_INSTRUCTION.TXT
- DECRYPT_INSTRUCTION.HTML
- DECRYPT_INSTRUCTION.URL
Step 9
Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_CRYPDEF.BUB. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.
Step 10
Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.
- database files
- web files
- MS Office files
- video
- images
- script files
- text files
- other non-binary files
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